Volume 7, Issue 3                                                                                                                        April 16, 1999


Vegetables

Vegetable Insects - Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Cabbage.

Begin scouting fields for the presence of imported cabbageworm and diamondback larvae during the next week. Imported cabbageworm butterflies can been seen laying eggs in fields. In the next 7 – 10 days, you should begin to see the first diamondback moths laying eggs on transplants. Young larvae will first mine between the upper and lower leaf surfaces before moving to the heart of the plants. Treatments should be applied when 5% of the plants are infested with larvae and before larvae move to the heart of the plants. Spin-Tor or a Bt insecticide will provide effective control.

Sweet Corn.

Be sure to check the earliest emerged sweet corn for cutworm and flea beetle activity. Treatments for cutworms should be applied if you find 10% leaf feeding or 3% cut plants in one-two leaf stage corn. Ambush, Asana, Pounce, or Warrior will provide effective control. Fields should be treated early in the morning or in the early evening when cutworms are close to soil surface to achieve the best control. With the warmer winter conditions and relatively dry soil conditions, the potential exists for heavier than normal flea beetle populations. Fields should be checked mid-day when beetles are active to get an accurate estimate of the population level. A treatment will be needed if 5% of the plants are infested with beetles. Ambush, Asana, Baythroid, Pounce, Sevin or Warrior will provide effective control.

 

Black Cutworm – Pheromone Trap Catches – 1999 Season

Data Provided by Terra Inc., Bridgeville, DE

Trapping Period: April 4 - 10, 1999

Location

#Moths/7 Days

Location

# Moths/7 Days

American Corner, MD

1

Lewistown, MD

7

Argos Corner, DE

5

Magnolia, DE

4

Atlanta, DE

3

Mardela Springs, MD

2

Bayard, DE

1

Marydel, MD

2

Berlin, MD

0

Milford, DE #1

22

Bethel, DE

0

Millsboro, DE

6

Bridgetown, MD

6

Milton, DE

2

Bucktown, MD

6

Newark, MD #1

3

Burrisville. MD

0

Newark, MD #2

0

Cambridge, MD

1

New Church, VA

3

Clarksville, MD

1

Oak Orchard, DE

0

Dagsboro, DE #1

1

Pocomoke, MD #1

4

Dagsboro, DE #2

0

Pocomoke, MD #2

0

Delmar, DE

16

Preston, MD

2

Denton, MD

4

Public Landing, MD

2

Easton, MD

0

Redden, DE

0

Eldorado, MD

0

Reeds Grove, MD

6

Ellendale, DE

6

Reliance, MD

1

Farmington, DE

5

Rhodesdale, MD

5

Federalsburg, MD

5

Ridgely, MD

1

Georgetown, DE

3

Seaford, DE #1

0

Goldsboro, MD

1

Seaford, DE #2

1

Greenwood, DE

1

Selbyville, DE #1

2

Hurlock, MD #1

5

Selbyville, DE #2

5

Hurlock, MD #2

1

Snow Hill, MD #1

2

Laurel, DE # 1

11

Snow Hill, MD #2

4

Laurel, DE # 2

4

Snow Hill, MD #3

4

Laurel, DE # 3

2

Trappe, MD

4

Leipsic, DE

3

Vernon, DE

1

Lewes, DE

1

Wyoming, DE

2

v


Avoid Gummy Stem Blight in the Greenhouse - Kate Everts, Extension Vegetable Pathologist, University of Delaware and University of Maryland; everts@udel.edu

Some watermelon and muskmelon transplants were infected with gummy stem blight (GSB) before planting in 1998. There are several greenhouse practices, which avoid or minimize infection by the GSB pathogen (Didymella bryoniae). The greenhouse should be disinfected before planting (benches, walls, walkways, etc.). The seed source should have tested negative for the pathogen with a minimum assay number of 1,000 seeds. Use clean transplant trays (disinfect trays if they will be reused) and new soil. Destroy any volunteer seedlings and keep the area in and around the greenhouse weed free. Avoid overhead watering if at all possible, or water in the middle of the day so that the plants dry thoroughly before evening. Keep relative humidity as low as possible through proper watering and good air circulation in the greenhouse.

As the seedlings develop, inspect them carefully. Infected seedlings will have small brown lesions on the leaves and water-soaked lesions on the stem. The lesion will become tan and have small black structures embedded in the stem (watermelon only). Initial infections will occur as ‘foci’ or clusters of diseased plants.

If the seedlings have lesions or appear diseased, destroy them and remove adjoining flats to a separate area for observation. Monitor these seedlings daily and destroy those that develop symptoms. Do not ship any trays containing plants with symptoms of GSB. Spray with a labeled fungicide when symptoms are observed and continue until plants are shipped. v

                                                             wpe1.jpg (7716 bytes)

        Gummy stem blight infected plants                                             Watersoaked lesion at the top of the seedling stem .

Pictures taken from: Diseases and Pests of Muskmelons and Watermelons, Richard Latin, Purdue Univeristy Cooperative Extension Service, West Lafayette, IN BP-44., 1993.


Field Crops

Field Crop Insects - Joanne Whalen, Extension IPM Specialist ; jwhalen@udel.edu

Field Corn.

During the past week, black cutworm moth activity increased significantly in the following areas: Delmar, Laurel and Milford, DE. These counts indicate areas where scouting should be concentrated, especially in situations with heavy broadleaf weed growth before planting. Be sure to scout early planted corn at plant emergence for cutworm leaf feeding activity. In general, the larvae present in early-planted corn are dingy cutworms, not black cutworm larvae. The moth counts found now will produce larvae and potential problems by early to mid-May. Rescue treatments should be applied if you find 10% leaf feeding or 3% cut plants in one to two leaf stage corn. A pyrethroid will provide effective control.

Small Grains.

Aphid populations continue to be moderate in most fields with higher populations found in barley fields.  We are starting to see low levels of cereal leaf beetle egg laying but no egg hatch has been observed. In the Beltsville area of Maryland, significant egg laying has occurred and egg hatch has started. If temperatures remain cool, no hatch should be expected until the last week in April. Controls will be needed once you find 25 eggs and/or larvae per 100 tillers with 50 –60 % egg hatch. True armyworm moth activity and egg laying remains low. The cumulative moth catches during April will give us an idea of the potential for problems.v


Field Crop Diseases - Bob Mulrooney, Extension Plant Patholgist ; bobmul@udel.edu                                        

Wheat.                                         

Early season diseases that may be present now are powdery mildew, Ascochyta leafspot, barley yellow dwarf virus, and soil-borne wheat mosaic virus. Powdery mildew is very easy to diagnose. Look for white to tan masses of fungal growth on the leaves. Powdery mildew continues to be the most common disease present. The amount varies considerably depending on the amount of nitrogen applied and varietal susceptibility. The cool weather pattern favors continued development, so continue to scout fields often. Jointing or growth stage 6 (Feeke’s), is a good time to begin checking for powdery mildew. Consider fungicide applications if 5-10% of the leaf area of the uppermost fully expanded leaves is infected. Fungicide applications will be most economically feasible when yield potential for the crop is in the 60 bushels/A and above range. If for some reason powdery mildew is out of control this early, these infected fields will likely lose substantial yield. Growers in this situation might want to put on a fungicide now in order to stop the powdery mildew before serious damage is done. If either Tilt or Quadris is applied now it will not provide control later if other diseases appear such as Septoria, tan spot, or rust. Tilt can only be applied once and two applications of Quadris would be too expensive. A possible solution may be to search out older stocks of Bayleton which have wheat on the label. It is legal to apply Bayleton to wheat as long as wheat is on the label. Bayleton applied at 2 oz/A will stop powdery mildew in its tracks and is a very economical treatment. Once you take care of the early powdery mildew problem, then you can reevaluate the crop and your late-season disease control needs as the season progresses. These situations only emphasize the importance of planting disease resistant varieties or using Baytan treated seed on powdery mildew susceptible varieties.

Ascochyta leafspot often appears at green-up and resembles Septoria leafspot. Symptoms include large gray-brown spots on the lower leaves that tend to be oval shaped. It will also produce small black to brown pinhead sized fungal structures in the dead leaf tissue. This fungus leafspot gets established on winter damaged tissue, but has been of minor importance and does not need to be controlled. This early in the season if you see circular areas in the fields where the wheat is shorter than the surrounding areas and lighter in color, barley yellow dwarf virus (BYD) or wheat soil-borne mosaic virus (WSBM) may be the cause. Closer observation may reveal that the oldest leaves are bright yellow, which may mean BYD, if leaves are mottled yellow-green it may indicate WSBM. The only way to be sure is to have a sample of infected plants tested for the presence of the virus. Aphids feeding in the fall and spring transmit BYD, WSBM is transmitted by a soil inhabiting fungus.

Soybeans.

Soybean severe stunt disease, which has only been identified in Sussex County, can be managed in several ways. Once this disease has been identified it can be managed by planting a non-host crop such as corn, sorghum, or vegetables, or plant a resistant soybean cultivar. We have identified several cultivars with resistance to SSSV. Group IV varieties with resistance include Delsoy 4710, Chesapeake, Corsica, Cisne, Agripro AP4400, Stine S4900, S4790, and Pioneer brand 9492, which is also Round-up ready. The resistant group V cultivars include Delsoy 5710 and Choska, which are very new and not available yet. Of these varieties Delsoy 4710, Delsoy 5710 and Pioneer brand 9492 have resistance to SSSV and the soybean cyst nematode races 3, 14. Our variety trial work has been partially funded by the Delaware Soybean Board and we are grateful for their support. This virus disease is soilborne and thought to be transmitted to soybeans by the dagger nematode. Yields from infected areas run anywhere from 5 to 20 bushels/A. Usually only small areas have plants that show the typical stunting and curling of infected leaves. The internodes are very short, and the leaves are crinkled and mottled. Infected areas can enlarge over time if the disease is not identified. It could be misdiagnosed as herbicide injury or early in the season you may think the plants have been grazed by deer, but on closer inspection you can see the dramatic symptoms. A new fact sheet on SSSV is now available at the county Extension offices and is available on the Web with full color pictures at http://bluehen.ags.udel.edu/deces/pp/pp-45/pp-45.htm.

Soybean seed treatments are good insurance when planting soybeans under adverse conditions. Planting into cool, wet soils especially in no-till and dry soils are situations where seed treatments would be beneficial. Normally seed testing 85% or better does not need seed treatment unless planting in adverse conditions. Seed germinating at 75% to 85% should be treated. Seed treatments containing captan, thiram, or carboxin are suggested. Many hopper-box treatments are also available. v


Grain Marketing Highlights - Carl German, Extension Crops Marketing Specialist; clgerman@udel.edu

Corn Stocks Raised; Soybeans Reduced.
The USDA monthly supply and demand reports released Friday, April 9th increased 1998/99 corn ending stocks 88 million bushels and reduced the estimate for soybean stocks by 40 million bushels. The corn market appeared to react relatively neutral to the increased estimate in ending stocks in lieu of the fact that traders were anticipating the increase. The reduction in soybean stocks was somewhat larger than anticipated, and has been reflected in the bidding for soybeans on the Board of Trade. Further support for soybean futures came from the reduction in the estimate for Argentina's soybean crop, reduced 500,000 metric tons.


Fundamentally, the ending stocks estimate for corn is bearish for the market. Higher stocks levels will tend to take some of the potential bidding frenzy out of the market in the event summer weather problems develop. The 1.799 billion bushel carryover estimate for corn is the largest stocks estimate in six marketing years. The next stocks estimates will be made in the July supply/demand report. For the time being, the market will now turn attention to planting conditions.

Maturing Loans Loom Large for Corn.
Large supplies of corn will be coming out of the 9-month government loans during late summer and early fall. That could spell trouble for corn prices if summer weather conditions turn out to be favorable. 114 million bushels of corn loans mature by the end of July, with another 1.206 billion bushels of corn loans maturing from August to October.


China Ends Import Ban on U.S. Wheat.
Significant wheat sales to China are not likely to happen anytime soon, China's domestic stocks remain large. The agreement reached by the U.S. and China hinges upon China's admittance into the World Trade Organization, which isn't expected to happen until the end of 1999.

Producer Marketing Strategy.
Current prices do not present great sales opportunities by any means. The two markets that command most of our attention at the moment are corn and wheat. Wheat futures are currently oversold, thereby presenting the possibility of a slight rally; maybe 10 to 15 cents per bushel from current levels. Sales for intended wheat production without a home will need to be considered at that time. New crop corn futures, having fluctuated about 10 cents per bushel since mid-December, still present some opportunity to lock-in a price that is somewhat better than the loan rate. For those that have previously forward priced a percentage of 1999 corn sales, hedging another 10 to 25% may be warranted. With the local soybean loan rate at $ 5.36 per bushel, it doesn't appear that sales are warranted at this time. v


Spring Forage Plantings - Richard W. Taylor, Extension Agronomist; rtaylor@udel.edu

We’re now in the middle of the spring forage planting window. But, to ensure success, growers should finish spring plantings as soon as possible. Early planting can be essential to success since we often experience both heat and dry weather in June or early-July. Both conditions can adversely affect forage establishment.

What other keys to success are there? A firm, well-prepared, weed-free (it’s essential to have all three conditions) seedbed or a weed-free, killed no-till cover crop with adequate crop residue is needed. Many forage seeds must be planted at a shallow depth to emerge and a good seedbed helps with seed placement and emergence. Having all weeds controlled before seeding also is critical since many forage grasses and legumes establish slowly and few, if any, weed control options are available to help or to rescue seedings.

Secondly, good fertility is essential. You should have pulled a soil sample and had it tested last fall for this spring’s plantings; but, if you did not, check and see if you have a recent soil test or a series of soil tests from the previous 3 to 5 years. By looking at the trend over the past several years or using a very recent soil test, you can obtain guidance for your fertility decisions. Most forage plantings last a number of years so fertility adjustments must be made prior to planting since thereafter only surface broadcast applications can be made.

What if you don’t have a recent soil test? Should you go ahead and plant anyway? Certainly, not your planned forage crop. Hold off on that planting until next fall or the following spring and between now and then soil test and add any needed fertilizer and lime. But, you need forage this year. Take your soil test now, have it analyzed, and apply the required fertilizer and lime later this spring. When the soil has warmed up, you can fertilize, work the ground, and plant one of the summer annual forage crops. These include sorghum-sudangrass hybrids, sudangrasses, foxtail and Japanese millet, hybrid pearl millet, soybeans (a late group V or maturity group VI as a hay crop), southern peas, and Brassica species. If you use very high nitrogen rates to increase dry matter production or if you use the sudangrass or sorghum-sudangrass hybrids, there are risks associated with production. Drought conditions after nitrogen application or even cool-cloudy weather if you are grazing can increase the risks of nitrate poisoning in the grass species. Sorghum, sudangrass, and sorghum-sudangrass hybrids should not be grazed if less than 18 inches tall because of the risk of prussic acid (HCN) poisoning (also in the fall, frost can cause a potential HCN hazard). Be sure you are familiar with the risks associated with whatever species you select for summer forage production. v


            Weather Summary

Week of April 8 to April 14

Rainfall:
0.64 inches: April 9, 1999
0.01 inches: April 10, 1999
0.31 inches: April 11, 1999
0.06 inches: April 12, 1999
Readings taken for the previous 24 hours at 8 a.m.
Air Temperature:
Highs Ranged from 81F on April 8 to 47 F on April 11.
Lows Ranged from 46F on April 9 to 36F on April 11.
Soil Temperature:
55 F average for the week.
(Soil temperature taken at a 2 inch depth, under sod)

Web Address for the U of D Research & Education Center:

http://www.rec.udel.edu


Compiled and Edited By:

Tracy Wootten

Extension Associate - Vegetable Crops


Cooperative Extension Education in Agriculture and home Economics, University of Delaware, Delaware State College and the United States Department of Agriculture cooperating, John C. Nye, Dean and Director. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Is the policy of the Delaware Cooperative Extension System that no person shall be subjected to discrimination on the grounds of race, sex, disability, age or national origin.


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